Notice that the offerings of the 12 tribes are the same, no matter how small or how large the tribe. Also notice that there are 12 tribes even though the tribe of Levi is not counted. Joseph is left out and his two sons Ephraim and Manasseh are in.

Aaron was told to set up the seven lamps that had been made according to the pattern God had given Moses on the mountain.
Num 8:2-4
"Speak to Aaron and say to him, 'When you set up the seven lamps, they are to light the area in front of the lampstand.'"Aaron did so; he set up the lamps so that they faced forward on the lampstand, just as the LORD commanded Moses. This is how the lampstand was made: It was made of hammered gold-- from its base to its blossoms. The lampstand was made exactly like the pattern the LORD had shown Moses.

Seven lamps are prominent elsewhere in Scripture as well.
Rev 4:5
From the throne came flashes of lightning, rumblings and peals of thunder. Before the throne, seven lamps were blazing. These are the seven spirits of God.

Everything was done by Moses just as the Lord commanded. So far…so good. Stay tuned!